Mercury arc converter



Oct. 7, 1941.

' D. H. DONALDSON ET AL MERCURY ARC CONVERTER Filed May 15, 1940 I mvam'rogzs A Dav/0 HHVRYDmVAwsmV HENRY 7170M!!! Emmy Patented Oct. 7, 1941 UNITED STATES MERCURY ARC CONVERTER David Henry Donaldson, North Wembley, and

. Henry Thomas Ramsay, Hatch End,'Pinner, England, minors to The General Electric Company Limited, London, England In reat Britain May 15, 1939 Applicatiog May 13, 1940, Serial No. 334,808 k 18 Claims.

This invention relates toan improvement in or modification of mercury arc converters of the type wherein a discharge occurs within a discharge envelope along an are from an anode to a mercury pool cathode, and, for initiating said discharge, means are provided for causing a 1 stream of'mercury-to issue from an orifice as a continuous jet impinging on an electrode within the discharge envelope, for causing an electric current to fiow along said jet, and for breaking said jet under the influence of an electric signal while said jet current is fiowing.

The essential feature of such converters is that they comprise means for causing a stream of mercury .to issue from an orifice within the envelope of the converter, normally as a continuous jet impinging on an electrode, and comprise, or

are adapted to be associated with. means forsource and the said electrode.

We have now realised that it is not necessary that the source should be insulated in the sense that there is a minimum permissible resistance between the source and the electrode. For an E. M. F. can be generated by magnetic induction A in a circuit that has substantially zero resistance;

but it is necessary, in order that a finite E. M. F. should be generated, that the circuit should have a finite impedance at the frequency oi" the inducing field.

Thus, as shown in the accompanying drawing,

i is the mercury cathode, I the anode, 3 the circuit providing the main discharge current, 4 the orifice from which the jet 5 issues and which is joined to the cathode by a channel 6 of very low resistance, consisting of a tube 'I through which the mercury is driven by the pump 8. A few turns 8 of the channel are linked with the ma netic core it, with which is also linked a primary winding ii, so that the turns 9, the core i0, and the winding ii form, a transformer. The ends of the winding i Lare connected with a D. C. supply I! through an interrupter it. When intermittent current is caused to fiow in the primary H by the operation of the interrupter it,

current will also flow in the path 6, so long as the jet isunbroken. The source I! and interrupter 55 I! may obviously be replaced by an A. 0. source the frequency and phase of which-are suitably related to those of the main circuit 3.

Conductance along the channel 6 may be pro- 5 vided mainly or wholly by the mercury in the channel; but this is not necessary; if the conductance lay mainly inthe walls of the channel, the current driven by the E. M. F. induced in the turn 9 would flow through the jet, where the walls necessarily have a gap, although little would flow through the mercury in the channel. According to the invention, in a mercury arc converter of the type specified, the said means for causing a current to fiow along the said jet comprises a conducting channel along which the mercury fiows between the said orifice and the said electrode, a transformer of which the said channel is the secondary, and means for causing 80 the strength of this current is too small to break I the jet by the pinch effect proper. Indeed if, in the arrangement shown in the said drawing, an impulsive voltage, lasting only a small'fraction of the period of the main supply I, is applied to 35 the primary ii, so that a pulse of current flows in the path 8 followed by a longer interval during which the current is much less than it is du'ring the pulse, the jet may be interrupted and the main discharge initiated after the said pulse of .40 current has ceased and during the said longer interval. The explanation is probably that the pulse starts a mechanical disturbance in the jet which leads to its instability, just as tapping the orifice might. Since a break in the jet will start 5 the main discharge, even when the current fiowing in the jet is quite small, it is possible by using this fact to start the main discharge by starting suddenly in the jet a current too small, or enduring for too short a time,- to break the jet by the 50 pinch effect.

7 According to a subsidiary feature of the invention, the said means for breaking the jetare means for starting in it suddenly a currentftoo small to break the jet by the pinch eifect.

The mean for thus breaking the jet may be an alternating or intermittent current to fiow in independent of the means for maintaining a current through it at the instant when it is broken. ,Thus, in the said drawing, theprimary ll might be fed from the supply I so that the current induced in the jet by this winding varies but slowly. An impulsive current, sufficient to set up the mechanical disturbance that breaks the let, might then be provided by other means, for example another winding on the core It or by connecting suddenly a charged condenser across-the secondary winding 8. I

The jet may also .be broken by other means. Thus, the jet may be permanently subjected to a transverse magnetic field and broken by the lateral force due to a current'through it; the currcnt'caused to flow along the jet may then be the electrical signal. Conversely, a constant current may be passed along it, and a transverse magnetic field established at the appropriate point in the cycle. Other methods will occur to those skilled in the art. Whether the current which is caused to flow in the primary ll be an intermittent current, an alternating current or an impulsive current, it is of a fluctuating nature and is deiined as fluctuating" in the annexed claims.

we claim:

1. In a mercury arc converter of the type wherein a discharge occurs within a discharge envelopeunlong an are from. an anode toa mercury pool cathode-means for. initiating said discharge-by causing a stream of mercury to flow along a conducting channel and to issue from an oriflce therein as a continuous jet impinging on said cathode, by causing a fluctuating current to ilow in the primary of a transformer of which the electro-dynamic forces generated by the mutual reaction oi the elements of said current, to such cross-section as to cause said Jet to break.

4. In a mercury arc converter of the type wherein a discharge occurs within a discharge envelope along an are from an anode toa mercury pool cathode, means for initiating said discharge by causing a stream of mercury to flow along a conducting channel and to issue from an oriflce therein as a continuous iet impinging on said cathode,- by causing a fluctatlng current to flow in the primary 0! a transformer of which said channel is the secondary, thereby causing an electric current to flow along said jet, and by breaking said jet under the influence of an electric signal while said Jet current is flowing by permanently subjecting said jet to a transverse magnetic field and breaking it by the lateral said channel is the secondary, thereby causing an I electric current to flow along said jet, and by breaking said let under the influence of an electric signal while said iet current is flowing.

2. In a mercury arc converter of the type wherein 'a discharge occurs within a discharge envelope alongan are from an anode to a mercury pool cathode, means for initiating said discharge by causing a stream of mercury to flow along .a conducting channel and .to issue from an oriflce therein as a continuous iet impinging on said cathode, by causing a fluctuating current to flow in the primary of a transformer of which said channel is the secondary, thereby causing an electric current to flow along said Jet, and by breaking said iet under the influence of an electric signal while said 'iet current is flowing by starting in it suddenly a current which, in itself, is

-insufllcient to contract the jet, under the electrodyn'a mic forces generated by the mutual reaction of the elements of said current. to such crossj oriflcetherein as a continuous 'iet impinging on saidcatliode, bycausing a fluctuating current to sectionas to cause said Jet to break.

, 3..In a mercuryarc converter of the type wherein a discharge occurs within a discharge envelope along an are from an anode to a mercury-pool cathode, means for initiating said discharge by causing a stream of mercury to flow alonga conducting channel and to issue from an flow in 'theprimary of a transformer of which said channel is the secondary, thereby causing an'electric current to'flow along said iet, and by breaking and iet'under the influence of an elec- 'tric signal while said jet current is flowing by starting in it suddenly a current which is independent ot the current maintained through the jet at the instant when it is broken and which, in itself, is insufllcient to contract the iet,under force due to a current through it.

5. In a mercury arc converter of the type wherein a discharge occurs within a discharge envelope along an are from an anode to a mercury pool cathode, means for initiating said dis charge bycauslng a stream of mercury to flow along a conducting channel and to issue from an orifice therein as a continuous jet impinging on said cathode, by causing a fluctating current to flow in the primary of a transformer 01 which said channel is the secondary, thereby causing an electric current to flow along said Jet, and by breaking said iet under the influence of an electric signal while said Jet current is flowing by former or which said'channel is the secondaryand with the primaryof which is connected a source of fluctuating electric current whereby an induced current is caused to flow along said jet between said oriflce and said cathode, and means for breaking said jet under the influence of an electric signal while said jet current is flowing.

"7. In a mercury arc converter of the type 1 wherein a discharge occurs within a discharge envelope along an are from an anode to a mercury pool cathode, means for initiating said discharge comprising a conducting channel for a stream of mercury, said channel being formed with an oriflce through which mercury issues as a' continuous Jet and impinges on said cathode, a transformer of .which said channel is the secondary and with the primary of which is connected asource of fluctuating electric current wherebyan. induced current is caused to flow along said jet between said oriflce and said cathode, and means.

for breaking said iet under the influence of an electric signal while said-Jet current is flowing by suddenly starting in said Jet current a current which, in itself, is insufflcient to contract the -iet, under the electrodyntmlc forces generated by the.

' mutual reaction of the elements of said current,

tosuch cross-sectionastocausesaldiettobreak. 8.In a mercury arc'converter-ofthe wherein a discharge occurs within a discharge" envelopealong an are from an anode to' a mercury pool cathode, means for initiating said discharge comprising a conducting channel for a. stream of'.

by suddenly starting in said jet current a current which is independent of the current maintained through the jet at the instant when it is broken and which, in itself, is insuflicient to contractthe jet, under the electrodynamic forces generated by the mutual reaction of the elements oi said current, to such cross section as to cause said jet to break.

9. In a mercury arc converter of the type 'wherein a discharge occurs within a discharge envelope along an are from an anode to a mercury pool cathode, means for initiating said discharge comprising a conducting channel for a stream of mercury, said channel being formed with an orifice through which mercury issues as a continuous jet and impinges on said cathode, a transformer of which said channel is the secondary and with the primary of which is. connected a source of fluctuating electric current whereby-an induced current is caused to flow along said jet between said orifice and said cathode, and means for breaking said jet under an orifice as a continuous jet impinging on an electrode within the discharge envelope; inductive means for causing an electric current to flow along said jet, said last named means including a-portion of said path; and means for breaking said jet while said jet current is flowing under the influence of an electric signal during successive cycles of the alternating current rectified by said converter so as to initiate a discharge in each of said cycles.

13. In a mercury arc converter of the type wherein a discharge occurs within a discharge envelope along an arc from an anode-to a mercury pool cathode, means for initiating said discharge, said means comprising the combination of means for causing a stream of mercury to new along a predetermined path and to issue from I an orifice as a continuous jet impinging on an electrode within the discharge envelope; and in-'- ductive means for passing a large fluctuating current throughsaid jet during successive cycles of the alternating current rectified by said converter so as to break said jet while said impulsive jet current is flowing and thereby initiate a discharge between the said anode and said cathode of said device'in each of said cycles, said last 7 named means including a portion of said'path.

cury pool cathode, means for initiating said disthe influence of an electric signal while said jetcurrent is flowing by permanently subjecting said jet to a transverse magnetic field and breaking it by the'lateral force due to a current through it.

10. In a mercury arc converter of the type wherein a discharge occurs within a discharge envelope along an are from an anode to a mer-, ciu'y pool cathode, means for initiating said discharge comprising a conducting channel for a stream of mercury, said channel being formed with an orifice through which mercury issues as 14. In a mercury arc converter of the type wherein a discharge occurs at regular temporal intervals along'an are from an anode to a mercharge at each of said intervals, said means comprising the combination of an orifice; means for causing a jet of mercury to flow along a predetermined path and to issue continuously from said orifice; inductive means for causing an electrio current to flow along said jet, said last named means including a portion of said path; and

means for breaking said jet at each of-said intervals while said jet current is flowing.

, 15. In a mercury arc converter oi-the typ a continuous jet and impinges on'said cathode, a

transformer of which said channel is the secondary and with the primary of which is connected a source of fluctuating electriccurrent whereby an induced current is caused to flow along said jet between said orifice I and said cathode, and means for breaking said jet under the influence of an electric signal while saidjet current is flowing by passing a constant current along said jet and establishing a transverse magnetic field at the appropriate point in the cycle.

11. In a mercury arc converter of the type wherein a. discharge occurs within a discharge envelope along an are from an anode to a mercury pool cathode, means for initiating said discharge, said means comprising the combination of means for causing astream of mercury to flow along a predetermined path and to issue from an orifice as a continuous jet impinging on an electrode within the discharge envelope; inductive means for causing an electric current to flow along said jet. said last named means including a portion of said path; and means for breaking said jet under the influence of an electric signal ,while the jet current is flowing.

12. In. a mercury arc converter of the type wherein a discharge occurs within a discharge envelope along an arc from an anode to a mercury pool cathode, means for initiating said discharge, said means comprising the combination of means for causing a streamof mercury to flow along a predetermined path and to issue from whereina discharge occurs at regular temporal intervals along an are from an anode to a mer-' cury pool cathode, means for initiating said discharge at each of said intervals, said means comprising the combination of an orifice; means for causing a jet of mercury to flow along a predetermined path and to issue continuously from said orifice inductive means for causing an electric current to flow along said'jet, said last named means including a looped portion of said path and a coupled inductance; and means for breaks ing said jet at each of said intervals while said jet current is flowing. I

16. In' a mercury arc converter of the typ breaking said jet at each of said intervals while said jet current is flowing.

17. In a mercury. arc converter of the type wherein a discharge occurs within a discharge envelope along an are from an anode to a mercury pool cathode, means for initiating said discharge, said means comprising the combination of a channel; an orifice insaid channel; means.

for causing a stream of mercury to flow along said channel and to issue i'r'om said orifice as a continuous Jet impinging on an electrode within the discharge envelope; inductive means, including a portion of said channel, to cause an electric current to flow along said stream and said Jet; and means to break said Jet while said current is flowing.

18. In a mercury arc converter of the type wherein a discharge occurs within a discharge envelope along an arc from an anode to a mercury pool cathode, means for initiating said discharge, said means comprising the combination of a channel; an orifice in said channel; means 10 to cyclically break said Jet;

DAVID HENRY DONALDSON. HENRY THOMAS RAMSAY; 

